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After a 24-hour blackout, Wikipedia has returned to full working order but declared: "We're not done yet."

The site had blocked its content for 24 hours in protest at proposed anti-piracy legislation in the US.

The encyclopaedia said the site had been viewed 162 million times, with eight million people following instructions to contact politicians.

The protest led to eight US lawmakers withdrawing their support for the proposed bills.

Two of the bill's co-sponsors, Marco Rubio from Florida and Roy Blunt from Missouri, are among those who have withdrawn their support after "legitimate concerns".

But backers of the legislation, led by the Motion Picture Association of America (MPAA), described the action as an "irresponsible" publicity "stunt".

The Stop Online Piracy Act (Sopa) and Protect Intellectual Property Act (Pipa) have caused considerable controversy among internet users and businesses since the plans were proposed in October last year.

'Melted servers'

Wednesday's co-ordinated action was intended to raise the profile of the debate to those outside of the tight-knit technology community - an objective Wikipedia said had been met.

"More than 162 million people saw our message asking if you could imagine a world without free knowledge," the site said.

Supporters of the bill were quick to condemn the actions of the websites. Ex-Senator Chris Dodd, MPAA's chief executive, described the blackouts as an "abuse of power".

Ahead of the day's action, Mr Dodd said: "It's a dangerous and troubling development when the platforms that serve as gateways to information intentionally skew the facts to incite their users in order to further their corporate interests."

Meanwhile, Creative America - a group which represents many big names in the movie business including Disney and Warner Bros - has launched an advertising campaign in the US.

A banner advertisement was shown in New York's Times Square offering advice on "what to do during an internet blackout". It suggested reading books, listening to music or watching a movie.

News Corporation chairman Rupert Murdoch, a vocal supporter of Sopa, continued to spar with users on Twitter.

He tweeted: "Seems blogsphere has succeeded in terrorising many senators and congressmen who previously committed. Politicians all the same."

Watching closely

In the UK, the plans around Sopa and Pipa have been keenly watched, particularly by those worried about the effect the measures could have on internet companies in the country.

Peter Bradwell, a campaigner with the Open Rights Group, told the BBC: "It's explicit that [Sopa advocates] want to tackle foreign websites.

A television advertising campaign supporting the anti-piracy plans has been launched

"We're concerned about the jurisdiction that gives over the kind of things you or I do on the internet in the UK - and the power that gives US copyright holders over the things that we do here."

Mr Bradwell recounted the comments made by Ed Vaizey, Minister for Culture, Communications and Creative Industries, who in July last year said he was looking at some anti-piracy measures being discussed in the US.

"Hopefully, what the storm around this has helped do is highlight why we are so concerned about proposals for new website blocking powers.

"I hope it really helps them understand how they shouldn't make policy, and really should drive home some of the complaints that we've been making."

'Startling'

The Department for Culture, Media and Sport said it did not wish to comment on the protests, nor on the details of Sopa and Pipa.

In pictures: Sopa protests

Eric Van Der Kleij, chief executive of the Tech City Investment Organisation, told the BBC: "We know that it is important for UK companies but it is definitely something for the US government. I am watching the situation closely.

"Regarding UK regulation, our position is that we are completely committed to an appropriate regulatory environment that protects rights but does not stifle innovation."

The UK's "digital champion" Martha Lane Fox said the blackout technique was surprising.

"Neutrality and equality of access is one of the fundamental principles of the internet," she told the BBC.

"So (while) I understand the concern that many US companies have about the restrictive Sopa law, blackouts are a startling way to show their frustration."

Constructive debate

Echoing the statements of rights holders in the US, Richard Mollet, chairman of the Publishers Association, criticised the blacked-out websites for not engaging "constructively" in the piracy debate.

"They should say: 'OK, there's a problem with copyright infringement. We, as internet companies, have a role here. What can we do to fulfil that role and help rights holders reduce infringement?'"

Creative America posted an image on Facebook of its advertisement on display in New York's Times Square

He argued that while Wikipedia was a valued resource, it would be more noticeable to the world if rights holders were to switch off their content for a day.

"Think what you would lose.

"If you walked around the streets of America or Britain with no creative content available to you, because rights holders had decided to shut up shop, you would be deprived of the BBC, cinemas, radio, bookstores and so on.

"What's at stake when rogue internet sites are available to people and revenues are deprived is a great deal more than the excellent but nevertheless more limited Wikipedia."